What's the smartest or most insightful thing you figured out as a kid that stays with you today?

I'm bad at decisions so I will name a few that stuck with me:

1. In 5th grade I realize that lines are hypothetical and all that really exists are line segments. (My teacher basically said yes, but you're confusing the class shut up.)
2. There are lies in all truths and truths in all lies. (A mantra I had).
3. The best way to get your way is to let someone else be the leader, act as the compromiser between the most disparate view points by saying you're adding ideas of both sides, but actually give your positions and lipservice to the others, then finally make it all seem like this was literally everyone else's idea and not yours. Ex. Working in a group project of 4 people to create a alternate energy model. A wants to make a wind turbine and it needs to be yellow. D wants solar panels made from copper. B just wants to do what's easiest. So you suggest a crank powered flash light that uses copper wiring, because it captures A's desire to have a kinetic energy conversion and using the copper wire shows D's desire to prove the usefulness of copper in alternative energy designs. A and D didn't say that's why they wanted the designs, but by making the argument in a good light and attributing it to them it makes them much more likely to go along. I believe my 4th grade teacher saw what I was doing as she had us do a lot of group work because after a while she had me do my own thing.